ESR-STM on diamagnetic molecule: C₆₀ on graphene

Area of Science:

• Surface Science
• Quantum Chemistry
• Spectroscopy

Background:

• Diamagnetic molecules typically lack electron spin resonance signals.
• Electron Spin Resonance-Scanning Tunneling Microscopy (ESR-STM) has been limited to paramagnetic species.
• Understanding molecular electronic structure and charge states is crucial for materials science.

Purpose of the Study:

• To demonstrate ESR-STM for diamagnetic C60 molecules on graphene.
• To correlate ESR-STM signals with molecular electronic structure and charge states.
• To establish ESR-STM as a general single-molecule identification technique.

Main Methods:

• Utilizing Electron Spin Resonance-Scanning Tunneling Microscopy (ESR-STM).
• Analyzing ESR-STM signals in relation to applied bias voltage.
• Correlating observed signals with molecular orbital ionization (LUMO and HOMO).

Main Results:

• Successful ESR-STM detection of C60 radical ion on graphene.
• Bias voltage-dependent ESR-STM signals reflecting C60 ionization.
• Identification of tip-related signals (WO3) and potential dimer/isotope signals.

Conclusions:

• ESR-STM can detect diamagnetic molecules, expanding its applicability.
• The technique provides insights into molecular charge states and electronic structure.
• ESR-STM offers a versatile method for single-molecule identification.